Gliederung

Venous function contributes to the pathogenesis of thrombophlebitis, venous thrombosis, and possibly to arterial hypertension. Venous disease is highly heritable; however, the genetic variance of venous function is unknown. We, determined the heritability of venous function in 46 twin pairs (24 monozygotic, age 35Â±11 yrs, 14 men, 34 women, and 22 dizygotic, age 30Â±8 yrs, 19 men, 25 women). After a resting phase in the supine position, we determined venous function in both legs by impedance plethysmography. Venous capacity was determined by a standardized protocol. In addition, we obtained venous pressure volume curves by slowly deflating a thigh cuff from 60 to 0 mmHg. Venous compliance was determined as the steepest part of the venous pressure volume curve. The "break-point" of the pressure volume relationship was determined manually. Venous capacity was 6Â±2.2 ml/100ml in monozygotic twins and 5.1Â±2.3 ml/100 ml in dizygotic twins. Venous compliance was 0.24Â±0.14 %/mmHg in monozygotic twins and 0.18Â±0.12 %/ mmHg in dizygotic twins. The breakpoint of the venous pressure volume curve was at a cuff pressure of 23Â±7.5 mm Hg in monozygotic twins and at a pressure of 26Â±8.9 mmHg in dizygotic twins. Heritability (h) was estimated using a path modeling approach. Unadjusted heritability (h2) was 0.6 (p<0.05) for venous capacity, 0.9 (p<0.05) for venous compliance, and 0.31 (ns) for the break point of the pressure volume curve. The heritability estimates remained essentially unchanged after adjustment for gender and age. We conclude that venous function is strongly influenced by genetic factors. The genes involved may influence venous disease states.